The last time life expectancy fell was in 1993 in the midst of the HIV/Aids epidemic. Drops have otherwise been rare as life expectancy has incrementally increased since the end of the Second World War.

Rises in death rates from heart disease, accidents (including drug overdoses), and Alzheimer’s disease were among the primary factors in the decline. There were also moderate increases in deaths from strokes, diabetes and suicide.

Of the ten leading causes of death only cancer killed fewer people as a portion of the population, with the death rate from influenza and pneumonia not changing significantly.

Life expectancy in 2014 versus 2015Credit:
NCHS

The drops in life expectancy between 2014 and 2015 are seemingly modest- from 76.5 years to 76.3 for men, and 81.3 to 81.2 for women, translating to one to two months on average - but the trends are worrying.

Jiaquan Xu, the lead author behind the new findings, said 2015 stood out as an “unusual” year.

“It looks like much more death than we have seen in the last few years," he told AFP.

More concerning still is that prior to 2015 life expectancy had been steady for three years, with growth slowing for decades before that.

Death rates in 2014 versus 2015 for ten leading causes of deathCredit:
NCHS

“There was already a pattern of unusually slow life expectancy growth in the United States that emerged in the 1980s,” Samuel Preston, a demographer at the University of Pennsylvania explained.

“What has happened recently is the pace of improvement has slowed even more, and now this is the first time in quite a while that there has actually been backsliding,” he said, noting that life expectancy continues to rise in Europe. In the UK it is 79.5 for men and 83.2 for women.

For those above 65 the death rate remained steady from 2014 to 2015, but it grew among those younger than 65. That increase is tied in large part to a spike in drug overdoses.

The only other drops over the past four decades came from 1992 to 1993 and 1979 to 1980, during an especially deadly flu outbreak, and could be attributed largely to a particular cause of death. That is not the case this time.

Death rates by race and genderCredit:
NCHS

While the rise in the death rate from heart disease was just 0.9 per cent, because it’s the leading cause of death even a small uptick translates to thousands of lives.

Deaths from Alzheimer's spiked 15.7 per cent in 2015, after an 8.1 per cent jump from 2013 to 2014.

Infant deaths from accidents also rose by 11.3 per cent. Mr Xu said most of the infants “died from accidental suffocation and strangulation in bed”.

The increase in death rates cut across races and genders, with black women as the only major demographic group for whom the rate did not rise. The biggest rise came among white women, with increases also found among both white and black men.